Knowledge on the reproductive biology of cassava, relevant to breeders and molecular geneticists, is still limited. Therefore, different studies were carried out to determine the duration of stigma receptivity and the rate of pollen tube growth. Inflorescences were covered for up to 3 days after the first opening of the bracts (e.g. anthesis day) to prevent open pollination. Results indicate that fruit and seed set are drastically reduced when flowers were covered for 2 or 3 days. However, fruits and seeds were obtained even from flowers that had been covered for 3 days after anthesis, although at low frequency. The rate of pollen tube growth was assessed in many combinations of female and male progenitors crossed through controlled pollinations and collecting the pistils at varying hours after pollination (HAP). Pollen tube growth is fast during the first 6 HAP reaching the tip of the nucellar beak. The growth slows down thereafter, taking 10 additional hours to reach the end of the beak. The growth of pollen tubes slows down even further until they enter the embryo sac. Only 10% of samples showed pollen tubes entering the embryo sac between 48 and 66 HAP. Although several tubes may reach the nucellar beak, only one was observed entering the embryo sac. Results, across the different experiments, were highly variable suggesting that the timeline of fertilization is influenced both by genotypic and environmental factors as well as the manual manipulation of inflorescences and cyathia.

Microdochium nivale is a fungal pathogen that causes yield losses of cereals during winter. Cold hardening under light conditions induces genotype-dependent resistance of a plant to infection. We aim to show how photosystem II (PSII) regulation contributes to plant resistance. Using mapping population of triticale doubled haploid lines, three M. nivale strains and different infection assays, we demonstrate that plants that maintain a higher maximum quantum efficiency of PSII show less leaf damage upon infection. The fungus can establish necrotrophic or biotrophic interactions with susceptible or resistant genotypes, respectively. It is suggested that local inhibition of photosynthesis during the infection of sensitive genotypes is not balanced by a supply of energy from the tissue surrounding the infected cells as efficiently as in resistant genotypes. Thus, defence is limited, which in turn results in extensive necrotic damage. Quantitative trait loci regions, involved in the control of both PSII functioning and resistance, were located on chromosomes 4 and 6, similar to a wide range of PSII- and resistance-related genes. A meta-analysis of microarray experiments showed that the expression of genes involved in the repair and de novo assembly of PSII was maintained at a stable level. However, to establish a favourable energy balance for defence, genes encoding PSII proteins resistant to oxidative degradation were downregulated to compensate for the upregulation of defence-related pathways. Finally, we demonstrate that the structural and functional integrity of the plant is a factor required to meet the energy demand of infected cells, photosynthesis-dependent systemic signalling and defence responses.

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